My daughter has dyslexia. You are right in pursuing diagnosis early, the earlier the diagnosis and intervention the better the outcome for the child! Do not let the school delay or convince you to wait!
I live in CT so, I really can't recommend anyone to you, but I can tell you how to find reliable resources and information.
Contact your states Learning Disability Association and Contact the National Dyslexia Association - you can call these association and they will provide you with free information and resources. At some point you may need to hire an advocate to help you navigate and "fight" the school system to get the services that your child has a right to if diagnosed with a learning disability.
Google Orton Gillingham, it is the gold standard for teaching kids with dyslexia, my daughter receives orton Gillingham tutoring outside of school and she now reads at grade level.
If you can get in touch with a tutor that specializes in Orton Gillingham method, they will beable to recommend someone that can test your son.
Read Sally Shaywitz's book - Overcoming Dyslexia - the book has a lot of useful information on dyslexia, diagnosis and intervention.
Oh, and google Masonic Learning Center and see if there is one in your area. My daughter receives free tutoring from them and they are dedicated to teaching kids with dyslexia and training people to tutor kids with dyslexia.
Thats is all that I can think of now, if you have any questions, please feel free to pm me.
L.
One other option for you, call the colleges in your area that have teaching programs, they will often test kids for free. This is a good choice because by the time the college student is pursuing special education classes they are already teachers and the professor over sees all the testing and reviews the results so you get two sets of eyes reviewing your childs results.